Electromechanical switching devices for switching electrical currents are known. One class of switching devices is represented by the so-called circuit breakers. These circuit breakers comprise a housing in which the individual phases of the currents are switched. The individual phases may be accommodated in pole cartridges, which are enclosed by a housing.
Moving and fixed contacts are accommodated in the pole cartridges, which moving and fixed contacts can be separated in order to open a power circuit and brought together in order to close the power circuits. During separation of moving and fixed contacts of a pole cartridge, an arc, which is typically quenched in a so-called “quenching chamber”, is formed. Likewise, circuit breakers are known which do not contain any pole cartridges and which accommodate moving and fixed contacts in their housing.
In circuit breakers, it is necessary in order to achieve good current limitation to quickly build up a high arc voltage. This is achieved with so-called “double-breaking interrupters”, which split the switching path twice and thus produce simultaneously two arcs in the event of a short circuit. The arc voltage produced by the arc is now present twice in the same time unit, which improves the current limitation in comparison with single-breaking interruption systems. Typically, in the case of these multi-breaking interrupter, two electrical contacts are arranged on a rotatably mounted contact bridges, which contacts represent the moving contacts. The two moving contacts interact with two fixed contacts of the electromechanical switching device so as to open and close the power circuit.
For example, DE 10 2013 208 373 A1 discloses a rotor for an electrical switch, comprising a rotor housing and a contact bridge which is rotatably mounted and which comprises two movable contacts, wherein by rotating the rotor the two movable contacts for closing or opening a power circuit may interact with two fixed contacts of an electrical switch, wherein the rotatably mounted contact bridge in the rotor housing is mounted so as to be movable in a direction which is perpendicular to the direction of the contact bridge in the closed position thereof.
DE 2009 052 965 B3 discloses an electromechanical switching device for in each case one pole of a low-voltage switching apparatus, comprising a rotary contact which is mounted in a rotor housing so as to be movable counter to a spring force and which is composed of at least one rotary-contact body which configures two lever arms, having in each case one lever-arm end, contact pieces being disposed on the mutually opposite lever-arm ends of the rotary-contact body, and in each case comprising fixed contacts which interact with the contact piece of each lever arm, wherein each lever arm is in each case impinged by a spring having a spring body, having in each case one support of a spring at one end on the rotary-contact body and another support at the other end on the rotor housing, wherein the respective support of the spring at one end is established at the at least one rotary-contact body by direct engagement on the rotary-contact body, and wherein both springs are disposed so as to be exclusively on one side of the rotary-contact body.
Double-breaking or multi-breaking electromechanical switching devices, having a rotary design, according to DE 10 2013 208 373 A1 or to DE 2009 052 965 B3, are susceptible to asymmetries. Asymmetry may be a result of the tolerance zone position of the component parts or of asymmetrical erosion during operation, whereby contact portions of the contact bridges may erode in an asymmetrical manner. This asymmetry leads to uneven contact forces and contact resistances at the contact portions and thus to a deterioration in the switching performance and/or in the electrical properties of an electromechanical switching device of this type.